''Caladenia caesarea'' subsp. ''transiens'', commonly known as the dwarf mustard spider orchid, is a plant in the orchid family Orchidaceae and is endemic to the

south-west The points of the compass are a set of horizontal, radially arrayed compass directions (or azimuths) used in navigation and cartography. A compass rose is primarily composed of four cardinal directions—north, east, south, and west—each se ...

of Western Australia. It has a single spreading, hairy leaf and up to three small lemon-yellow flowers with red stripes. It is only known from a single small population near the town of Williams.

Description

''Caladenia caesarea'' subsp. ''transiens'' is a terrestrial, perennial, deciduous,

herb In general use, herbs are a widely distributed and widespread group of plants, excluding vegetables and other plants consumed for macronutrients, with savory or aromatic properties that are used for flavoring and garnishing food, for medicinal ...

with an underground tuber and a single erect, hairy leaf long and about wide. There are up to three lemon-yellow flowers borne on a stem high and each flower is long and wide. The lateral sepals and

petal Petals are modified Leaf, leaves that surround the reproductive parts of flowers. They are often advertising coloration, brightly colored or unusually shaped to attract pollinators. All of the petals of a flower are collectively known as the ''c ...

s spread widely. The labellum is lemon-yellow coloured with brownish-red stripes, projects prominently with a curled tip, has an irregularly serrated edge and two rows of shiny yellow calli along its centre. Flowering occurs between September and October and is followed by a non-fleshy,

dehiscent Dehiscence is the splitting of a mature plant structure along a built-in line of weakness to release its contents. This is common among fruits, anthers and sporangia. Sometimes this involves the complete detachment of a part; structures that op ...

capsule containing a large number of seeds.

Taxonomy and naming

This orchid was formally described by Karel Domin in 1912 and given the name ''Caladenia filamentosa'' subsp. ''caesarea''. Domin's description was published in ''

Journal of the Linnean Society, Botany The ''Botanical Journal of the Linnean Society'' is a scientific journal publishing original papers relating to the taxonomy of all plant groups and fungi, including anatomy, biosystematics, cytology, ecology, ethnobotany, electron microscopy, ...

'' but in 1989 Mark Clements and

Stephen Hopper Stephen Donald Hopper AC FLS FTSE (born 18 June 1951) is a Western Australian botanist. He graduated in Biology, specialising in conservation biology and vascular plants. Hopper has written eight books, and has over 200 publications to his n ...

raised it to species status. In 2001 Hopper and Andrew Brown described three subspecies, including subspecies ''transiens'' and the descriptions of these subspecies were published in '' Nuytsia''. The

epithet An epithet (, ), also byname, is a descriptive term (word or phrase) known for accompanying or occurring in place of a name and having entered common usage. It has various shades of meaning when applied to seemingly real or fictitious people, di ...

(''transiens'') alludes to the shape of the labellum, which is intermediate between that of ''

Caladenia filamentosa ''Caladenia filamentosa'', commonly known as daddy-long-legs, is a plant in the orchid family Orchidaceae and is endemic to eastern Australia. It is a ground orchid with a single hairy leaf and up to four, usually dark red flowers with long, ...

'' and the other subspecies of ''Caladenia caesarea''.

Distribution and habitat

Dwarf mustard spider orchid only occurs near Williams in the Jarrah Forest

biogeographic region An ecoregion (ecological region) or ecozone (ecological zone) is an ecologically and geographically defined area that is smaller than a bioregion, which in turn is smaller than a biogeographic realm. Ecoregions cover relatively large areas of l ...

where it grows under dense

rock sheoak ''Allocasuarina huegeliana'', commonly known as rock sheoak or sighing sheoak, is a tree in the family Casuarinaceae. Endemic to Western Australia, it occurs mostly throughout the Wheatbelt region. It is now especially common on road verges, w ...

and

wandoo Wandoo is the common name for a number of Western Australian ''Eucalyptus'' species, all of which have smooth white bark. The original "wandoo" is ''Eucalyptus wandoo''. Additional species have been given this name because of a perceived likeness w ...

trees.

Conservation

''Caladenia caesarea'' subsp. ''transiens'' is classified as " Priority One" by the Government of Western Australia

Department of Parks and Wildlife The Department of Parks and Wildlife (DPaW) was the department of the Government of Western Australia responsible for managing lands described in the ''Conservation and Land Management Act 1984'' and implementing the state's conservation and e ...

, meaning that it is known from only one or a few locations which are potentially at risk.

References

{{Taxonbar, from=Q21382904

caesarea Caesarea () ( he, קֵיסָרְיָה, ), ''Keysariya'' or ''Qesarya'', often simplified to Keisarya, and Qaysaria, is an affluent town in north-central Israel, which inherits its name and much of its territory from the ancient city of Caesare ...

Endemic orchids of Australia Orchids of Western Australia Plants described in 2001 Taxa named by Stephen Hopper